It is proposed to investigate the molecular mechanisms involved in the hormonal induction and regulation of fatty acid synthetase and acyl-CoA desaturase in chick embryo liver, rat liver and cultured liver explants. The requirements of different components in culture medium for the induction of synthetase and delta 9 and delta 6 desaturases in cultured liver explants will be evaluated. Antibodies to purified terminal desaturase will be used to quantitate the amount of desaturase protein in newly hatched chicks with different nutritional status and in induced liver explants and cultures. Synthesis and turnover of the terminal desaturase in neonatal chicks, rat liver and cultured liver explants will be measured by immunochemical techniques. The rates of synthesis and degradation of the synthetase and terminal desaturase in insulin, insulin plus thyroxine and hydrocortisone induced liver preparations will be related to the amount of these enzymes by immunochemical methods. Hormonal induction of fatty acid synthetase in embryo liver and cultured liver explants will be related to the amount of polysomes synthesizing fatty acid synthetase and to the levels of fatty acid synthetase and to the levels of fatty acid synthetase mRNA as measured by cell-free fatty acid synthetase synthesis by rabbit reticulocyte lysate.